A marine craft, such as a boat floating in water, or a marine structure, such as a dock or a water system intake, each have surfaces that are submerged in water, thereinafter referred to as "marine surfaces". Due to their submergence in water, these marine surfaces may be affected by many types of biotic fouling contaminates. Ultimately, these biotic fouling contaminates must be physically cleaned from the marine surfaces, often at a great expenditure of labour and time.
These contaminates commonly include algae, crustaceans such as barnacles, tube worms and the like. Initially, only algae attach to the submerged marine surfaces of a marine craft or marine structure. In the case of a marine craft, the submerged surfaces include the hull and the running gear. While the formation of algae on the submerged marine surfaces may potentially be problematic, it is usually only a minor problem in most marine areas, since algae grows at a relatively slow rate.
A much more significant and serious problem is the large scale accumulation of crustaceans such as zebra mussels, barnacles, tube worms, and the like on marine surfaces. Zebra mussels, barnacles, tube worms and the like, attach themselves, in their larvae stage, to marine surfaces that have algae growing on them in order to eat the algae, as algae is a food base for such larvae. These crustacean larvae continue to feed and grow into their adult stage, where they remain attached to the same marine surface, until physically and forcibly removed.
An extremely large number of any of these larvae may attach themselves to algae covered marine surfaces due to the relatively small size of the crustacean larvae. The larvae grow quite quickly on the submerged algae covered marine surfaces, and in the matter of a few weeks, or possibly one to two months, the growing crustaceans, which may include zebra mussels, barnacles, tube worms and the like, can cover virtually all of the submerged marine surfaces of a marine craft or marine structure.
In the case of a marine craft, significant formation of algae, zebra mussels, barnacles, tube worms and the like on the hull of a boat tends to slow a boat down significantly for any given power setting, or alternatively, tends to cause very significantly increased gas consumption, corresponding to an increased power setting, which increased power setting would be required in order to maintain a given speed. The moving parts of the marine craft, such as the running gear, become more difficult to move and tend to experience a decreased range of movement. Any intakes on a marine craft, such as a water intake for the cooling system, may be partially blocked or fully blocked, which may eventually lead to problems such as engine overheating. Further, accumulations of algae, zebra mussels, barnacles, tube worms and the like on a marine craft are aesthetically displeasing.
In some areas of North America, it is required by law to have a marine craft power washed to remove zebra mussel and other biotic fouling contaminants before it is allowed to pass from one body of water, such as a lake, to another body of water. This requirement is intended to prevent the spread of zebra mussels. However, such a requirement is a great inconvenience to boaters, and also is an unwanted expense.
In order to remove zebra mussels, barnacles, tube worms and the like from a boat, they must be scraped off after the boat has been raised out of the water and placed in a dry-dock, or the like, which is a very difficult and time consuming task. The algae that remains thereon can then be washed off with a suitable cleaning substance. This process of removing the zebra mussels, barnacles, tube worms and the like is very inconvenient since the boat cannot be used for a period of time. Moreover, is relatively expensive, and must be re-done every few months, or possibly even every few weeks in warmer waters where fouling occurs more rapidly. Further, algae, zebra mussels, barnacles, tube worms and the like start forming immediately after the boat has been returned to the water, and a significant number can be attached to the cleaned boat within weeks or even days of such return.
Of more recent concern is the geographic spreading of crustaceans from native waters to waters where such crustaceans have few, or no, natural predators or parasites. Resultingly, such crustaceans are allowed to grow virtually unhindered, and can accumulate at alarming rates. Unfettered accumulations of such crustaceans can become significant, extremely quickly. Zebra mussels are not native to North America, but have been recently introduced into many North American waterways, and are geographically spreading quite rapidly. While zebra mussels are of concern even in their native waters, their presence is of very serious concern in North America.
Various conventional preventative measures have been used to preclude the formation of algae, zebra mussels, barnacles, tube worms, and the like on marine craft. A very common and partially successful way of precluding formation of algae, zebra mussels, barnacles, tube worms and the like on boats is anti-fouling paint, which is usually tin based or copper based. While these types of anti-fouling paints work reasonably well, the metal base of the paint slowly leaches into the water, thereby causing an environmental hazard. Resultingly, metal based anti-fouling paints have been banned from use by many governmental authorities.
Anti-fouling waxes may also be used with a reasonable degree of success to preclude the formation of algae, zebra mussels, barnacles, tube worms and the like. While these anti-fouling waxes do not create the environmental hazard represented by anti-fouling paints, they typically wash off within about one month or less. A further disadvantage of anti-fouling waxes is that the boat must be put into a dry-dock each time the wax is to be applied, which again is inconvenient, time consuming and expensive. Also, anti-fouling waxes are relatively expensive when used on a regular basis.
A more recent technology for precluding the growth of algae, zebra mussels, barnacles, tube worms, and the like on marine surfaces is by way of ultrasonic transducers. In use, one or more transducers, in the form of a diaphragm or magnet, are attached to, for example, the inside of the hull of a boat. The transducers are vibrated ultrasonically. This ultrasonic vibration causes the hull of the boat to vibrate ultrasonically, which thereby causes a thin layer of water adjacent the hull of the boat to also vibrate ultrasonically. Such ultrasonic vibration of the thin layer of water adjacent to the hull of the boat does not preclude algae from reaching the boat; however, it does, at least initially, preclude the zebra mussels, barnacles, tube worms and the like from reaching the initial thin layer of algae on the boat. Notwithstanding this, however, the algae continues to grow on the submerged marine surfaces of the boat, to the point where the thickness of the algae layer eventually exceeds the thickness of the ultrasonically vibrated layer of water. At this point, zebra mussels, barnacles, tube worms and the like can then begin to feed on the outer layers of algae. As the zebra mussels, barnacles, tube worms and the like grow, they become strong enough to attach to the ultrasonically vibrating submerged marine surfaces of the boat. Resultingly, it has been found that ultrasonic transducers are not overly effective in precluding the growth of algae, zebra mussels, barnacles, tube worms, and the like on marine surfaces.
Other problems with ultrasonic anti-fouling systems have also been found. Various parts of the running gear are not vibrated sufficiently, unless one or more transducers are placed directly on each part. Further, the outer bearing on the propeller shaft of a marine motor is typically made from rubber or similar resilient material, and therefore readily absorbs ultrasonic vibration. Thus, marine propellers cannot be protected to any significant degree from biotic contamination of the type discussed herein by way of ultrasonic anti-fouling devices.
Further, ultrasonic transducers are relatively expensive and are audibly detectable during operation, which is annoying.
It has been found that by continuously or intermittently causing a flow of water of a speed greater than about four miles per hour along a submerged marine surface, the formation of marine plants and animals such as algae, zebra mussels, barnacles, tube worms and the like can be substantially precluded. The frequency of use of the above stated means of precluding the formation of marine plants and animals such as algae, zebra mussels, barnacles, tube worms and the like is influenced by the severity of the local fouling conditions of the water, including salinity, Ph level, and temperature, among other factors.
It is an object of the present invention to provide an anti-fouling device for marine surfaces that substantially precludes the attachment of algae, zebra mussels, barnacles, tube worms and the like to such surfaces.
It is another object of the present invention to provide an anti-fouling device for marine craft which device precludes the need for the craft to be removed from the water in order for the device to be operative.
It is a further object of the present invention to provide an anti-fouling device for marine surfaces which device does not present an environmental hazard to the marine environment in which it is utilized.
It is an object of the present invention to provide an anti-fouling device for marine surfaces that is relatively inexpensive to operate on an ongoing basis.
It is an object of the present invention to provide an anti-fouling device for marine surfaces that is relatively simple to manufacture and install and which is, therefore, relatively inexpensive.
It is a further object of the present invention to provide a method for retarding the formation of marine plants and animals on marine surfaces submerged in water which is relatively simple and economical to perform and which is more effective over previously used methods.